OBJECTIVE: To ascertain the role and mechanisms of action of insulin on growth and functions of experimental mammary tumors. APPROACH: Two rodent mammary tumors are being studied: (1) R3230AC tumor responsive but not dependent on insulin and (2) DMBA-induced tumors dependent on insulin. Two aspects are being examined: (1) characterization of specific insulin binding and (2) elucidation of insulin-induced action on these cells by examination of glucose, and amino acid transport and metabolism and investigation of changes in cAMP and cGMP to seek out correlations with growth behavior of neoplasms. Experiments employ insulin in vivo, by use of appropriately modified tumor-bearing hosts, i.e. diabetic, intact, and by use of dissociated tumor cells exposed to insulin in vitro.